Italian lawmakers have claimed Amanda Knox was treated unfairly during her murder trial and have called for a probe of the prosecutor's office in Perugia.

Led by Rocco Girlanda, a group of MPs has sent a letter and petition to the Italian president casting doubt on the prosecution's case in the U.S. student's conviction.

They allege than an appeals trial currently under way in Perugia has undermined the reliability of evidence originally collected against Knox - from Seattle, Washington.

They also maintain she should not have been kept behind bars since her arrest.

Mr Girlanda said in the letter: 'These distortions, not without reason, are fuelling accusations against the administration of justice in our country.'

The request has been spearheaded by Mr Girlanda, an Italian MP who has frequently visited Knox in prison and has written a book about her.

The petition to Justice Minister Angelino Alfano was signed by 11 lawmakers - all members of Premier Silvio Berlusconi's coalition.

It asks Mr Alfano to consider sending inspectors to judicial offices in Perugia - where British student Meredith Kercher was killed in the flat she shared with Knox.

Knox was arrested on November 6, 2007, four days after the body of Ms Kercher was found hidden under a blanket. The 21-year-old had been stabbed to death.

Knox was jailed for 26 years and Sollecito for 25. The two have always denied involvement in her murder. Read More